Although extensive research exists on vocabulary instruction during book reading in preschool classroom, comparatively little research has been conducted on vocabulary exposure in classroom play contexts and child vocabulary outcomes. The purpose of this study was to examine Head Start teacher and child vocabulary use in dyadic play sessions and the relation between teachers' vocabulary use and children's vocabulary outcomes. One Enhanced Milieu Teaching (EMT) session for each of 53 teacher-child dyads was transcribed and coded for teacher use of target and sophisticated vocabulary, use of teacher strategies to support vocabulary development, and child use of vocabulary. Descriptive data indicate variability for both teacher and child vocabulary use in the play sessions. Both teacher total number of vocabulary words and vocabulary supports were significantly related to child vocabulary use within sessions. Implications for practice are discussed.